Conventionally, there has been provided a special effect device (DVE: Digital Video Effects) which gives video signal the special effects such as, cropping of image (Crop), skewing (Skew), and variation in the X-axis direction and the Y-axis direction (XY-rate) to transform an image. It has been considered that the device is used to obtain "Slab" effect for displaying an image on a face of a rectangular parallelepiped formed in a three-dimensional space.
More specifically, as shown in FIG. 1, in the "Slab" effect processing, a moving picture displayed on a two-dimensional plane is referred to as an object image (Object), and the special effect device is used to form an image that the object image seems to be stuck to an object image displaying face (SideA) of a rectangular parallelepiped formed in a three-dimensional space.
In the "Slab" effect, as well as the face on which the object image is displayed (SideA), two side faces (SideB and SideC) are simultaneously displayed in accordance with an inclination of the rectangular parallelepiped in a three-dimensional space. FIG. 2 shows a method of forming the three-dimensional six-side display image by using one special effect device (DVE).
That is, in FIG. 2, a first video tape recorder (VTR) 6 is used to reproduce an object image (Object) which is output to a special effect device 5. The special effect device 5 performs the mapping processing in which the reproduced object image (Object) seems to be stuck to the object image displaying face (SideA) of the three-dimensional six-side display image, which is output to a second video tape recorder (VTR) 7. The second video tape recorder 7 records the object image displaying face (SideA) being the object image (Object).
An operator reproduces by a third video tape recorder 8 a video tape in which the object image displaying face (SideA) is thus recorded, and outputs it to a composing circuit 9. At this time, the operator also reproduces, on a two-dimensional plane by the first video tape recorder 6, an image to be displayed on the side face (SideB) of the three-dimensional six-side display image. The image reproduced by the first video tape recorder 6 is output to the special effect device 5 and the special effect processing is performed on it.
Thus, the image on a two-dimensional plane reproduced by the first video tape recorder 6 is transformed into the shape which seems to be displayed on the side face (SideB) of the three-dimensional six-side display image. The image of side face (SideB) is composed with the object image displaying face (SideA) at the composing circuit 9. At this time, the operator uses a specified operation key to adjust the display position so that the object image displaying face (SideA) and the side face (SideB) are close at one edge each other. The composed image of the object image displaying face (SideA) and the side face (SideB) obtained at the composing circuit 9 is recorded at the second video tape recorder 7.
The operator reproduces at the third video tape recorder 8 the video tape in which the composed image of the object image displaying face (SideA) and the side face (SideB) is recorded, and outputs it to the composing circuit 9. At this time, the operator also reproduces the image to be displayed on the side face (SideC) of the three-dimensional six-side display image on a two-dimensional plane by the first video tape recorder 6. The image reproduced by the first video tape recorder 6 is output to the special effect device 5 and the special effect processing is performed on it.
Thus, the image on a two-dimensional plane reproduced by the first video tape recorder 6 is transformed into the shape which seems to be displayed on the side face (SideC) of the three-dimensional six-side display image. The image of side face (SideC) is composed with the composed image of the object image displaying face (SideA) and the side face (SideB) at the composing circuit 9. At this time, the operator uses a specified operation key to adjust the display position so that the object image displaying face (SideA) and the side face (SideB), and the object image displaying face (SideA) and the side face (SideC) are respectively close at one edge each other.
The three-dimensional six-side display image obtained at the composing circuit 9 is recorded at the second video tape recorder 7.
By the way, in the case of forming the three-dimensional six-side display image by using the above method, the side faces (SideE and SideC) are formed separately from the object image displaying face (SideA) for displaying an object image (Object) and are composed. Accordingly, when the inclination of three-dimensional six-side display image is changed in a three-dimensional space, even if the special effects such as, cropping of image (Crop), skewing (Skew), and variation in the X-axis direction and the Y-axis direction (XY-rate), on the object image displaying face (SideA) are changed, the side faces (SideB and SideC) are not followed. Therefore, it is also needed to change the special effects to the side faces (SideB and SideC) in accordance with the change of the object image displaying face (SideA) in the three-dimensional space.
In this case, an operator has to perform the work of composing the side faces (SideB and SideC) manually for each frame (60 frames per second) in accordance with the change of the object image displaying face (SideA). There has been a problem that the operation of operator becomes complicated.